Turbine oil antioxidants



Dec. 14, 1954 H. D. NORRlS ET AL 2,697,074

TURBINE OIL ANTIOXIDANTS Filed Feb. 7, 1952 United States Patent TURBINE on. ANTIOXIDANTS Henry D. Norris, Woodbury, and Ralph V. White, Pitman, N. J., assignors to Socony-Vacuum Oil Company, Incorporated, a corporation of New York This invention relates broadly to mineral lubricating oils containing organic nitrogen compounds. It is more specifically concerned with such mineral lubricating oils having improved resistance to oxidation.

As is Well known to those skilled in the art, most lubrieating oils are subject to oxidation during use. In the case of highly-refined oils, such as those used to lubricate steam turbines, attack by atmospheric oxygen at elevated temperatures is most pronounced. Such attack occurs especially readily in the presence of catalytic metals, such as iron, copper and copper alloys, which are encountered in most lubrication systems. The deleterious results of such oxidation are manifested by the formation of acidic substances, colored oxidation products, and sludge. It will be obvious to those skilled in the art that such conditions cannot be tolerated in fine machinery, such as steam turbines.

It has now been found that the oxidation tendencies of mineral lubricating oils can be sharply inhibited by the addition thereto of a novel type of antioxidant. It has now been discovered that the certain arylethylamines, when added to mineral lubricating oils in small amounts, increase the resistance thereof to oxidation.

Accordingly, it is a broad object of the present invention to provide novel antioxidants. Another object is to provide mineral lubricating oils containing effective antioxidants. A specific object is to provide mineral lubri cating oils containing certain arylethylamines in small amounts. Other objects and advantages of the present invention will become apparent to those skilled in the art, from the following detailed description.

In general, this invention provides a mineral lubricating oil containing a small amount, suflicient to inhibit the oxidation tendencies thereof, of a compound having the formula:

wherein Y is an unsubstituted, aromatic hydrocarbon radical, R and R are alkyl groups having between 1 and 8 carbon atoms, and n is an integer of between 2 and 3, inclusive.

The compounds utilizable herein can be prepared readily. One type, wherein n in the above formula is 2 can be produced by reacting an alkylarylamine with a di(;3-haloethyl)alkylamine hydrohalide in a molar proportion of 2:1, respectively. The other type, wherein n in the above formula is 3, is obtained by reacting an alkylarylamine with a tri(,8-haloethyl)amine hydrohalide, in a molar proportion of 3:1, respectively. The reactions involved, in each case, proceed in accordance with the following equations, using ethylaniline as the alkylarylamine reactant:

C 2115 (ON-CHaCHzhN 411x As will be apparent from the general formula set forth hereinbefore, the alkylarylamine reactant, a secondary amine, is subject to two restrictions. Firstly, the aromatic ring (Y in the formula) must be unsubstituted. The presence of substituent groups, such as hydroxyl, alkoxy, nitro, halo radicals and the like detract from the antioxidant properties of the ultimate compounds contemplated herein. In fact, even alkyl substituents cannot be present on the aromatic ring. Secondly, the alkyl group (R in the formula) attached to the nitrogen atom must contain between 1 and 8 carbon atoms. It can, however, be a straight-chain or a branched-chain alkyl group. Accordingly, non-limiting examples of the alkyl arylamine reactant are N-ethylaniline, N-ethyl-l-naphthylamine, N-isoamylaniline, N-methyl-Z-naphthylamine, N-t-amylaniline, N-methylaniline, N-propyl-l-naphthylamine, N-butylaniline, N-isopropylaniline, N-isoheptylaniline, N-Z-ethylhexylaniline, N-isobutyl-Z-naphthylamine, N-octyl-l-naphthylamine, N-methyl-l-anthrylamine, N- butyl-2-anthrylamine, N isohexyl l anthrylamine, N- propyl-9-anthrylamine, N-methyl-Z-phenanthrylamine, N- ethyl-3-phenanthrylamine, and N-ethyl-9-phenanthrylamine.

The tri([3-haloethyl)amine hydrohalide reactant, can have a bromo, chloro or iodo atom as the halo group therein. Thus, the reactant can be tri(,B-chloroethyl)- amine hydrochloride, tri( 9-bromoethyl)amine hydrobromide, or tri( 3-iodoethyl)amine hydroiodide. The (ii-(,3- hal0ethyl)alkyl amine hydrohalide can have any halogen atom therein, as aforedescribed for the trihaloethyl reactant. The alkyl radical thereof (R' in the general formula) must contain between 1 and 8 carbon atoms. This radical can be a straight-chain or a branched-chain alkyl group. Non-limiting examples of the alkyl radicals R) of these amines are methyl, propyl, isopropyl, ethyl, butyl, isobutyl, t-butyl, amyl, sec-amyl, hexyl, isoheptyl, octyl, and Z-ethylhexyl radicals. As is well known to those skilled in the art, these amines can exist in the free state. However, they are not too stable and readily form quaternary salts. In addition, the free amines are extremely toxic. Accordingly, although use of the free amine is contemplated, the amine will be used in the form of the hydrohalide in practical application.

It will be noted that the reactions illustrated in Equations 1 and 2 proceed with the formation of hydrogen halide. In order to ensure complete reaction, in accordance with the principle of Le Chatelier, the hydrogen halide should be removed or chemically immobilized. This can be effected by having suflicient hydrogen halide acceptor present in the reaction system to combine with the hydrogen halide. Amines are often used for this purpose, forming the amine hydrohalide. This amine can be an excessive amount of the alkylarylamine reactant, or it can be another amine, preferably a tertiary amine. Thus, for example, in Equation 1 5 moles of N-ethyl aniline could be used, i. e., two moles for the principal; reaction and the other three moles to react with the hydrogen halide. Alternatively, three moles of a suitable hydrogen halide acceptor can be used. Suitable hydrogen halide acceptors include trialkylamines (tributylamine triamylamine, triethylamine, etc.), heterocyclic nitrogen compounds (pyridine, piperidine, etc.), primary and secondary aromatic amines (aniline, toluidine, diphenyl-' amine, etc.), inorganic bases (sodium carbonate, sodium bicarbonate, etc.), and many others well known to those skilled in the art.

The reaction between the alkylarylamine reactant and the haloethylamine reactant is eifected at a temperature of between about C. and about 240 0., preferably, between about 200 C. and about 230 C. The time of reaction, of course, is dependent upon the temperature selected and the particular reactants involved. In general, the reaction is complete in between about 3 hours and about 15 hours.

Separation of the desired compound from the reaction product is readily effected. Amine hydrohalides, excess reactants, etc. can be removed by filtration and/ or distillation methods. The compound formed by the reaction is in the residue after the distillation operation. It can be tion, recrystallization, etc.

The following specific examples are presented for the purpose of illustrating the compounds of this invention and of demonstrating their effectiveness as antioxidants in mineral lubricating oils. it must be strictly understood that this invention is not to be limited to the specific compounds used in the examples, or to the operations and manipulations involved. As will be apparent to those skilled in the art, a variety of other compounds, as de fined hereinbefore, are also utilizable.

EXAMPLE 1 N,N-di[}8-(N phenyl-N ethylammo)ethyl] -n-butylamine N-ethylaniline and N,N-di(fi-chloroethyl)-n-butylamine hydrochloride, in a molar proportion of 6:1, respectively, were heated together at 210 C. for 8 hours. Then, the reaction mixture was cooled and made strongly alkaline by the addition of 10-per cent aqueous sodium hydroxide. This mixture was then steam distilled until 100 milliliters of distillate showed no N-ethylaniline was distilling over. The cooled residual product was dissolved in 250 milliliters of diethyl ether and washed with water. The ether was removed by evaporation on the steam bath, leaving the product, N,N-di[fi-(N-phenyl-N'-ethylamino)- ethyl] -n-butylamine.

EXAMPLE 2 T riifi-(N-phenyl-N-ethylamin)ethyl] amine N-ethyl aniline and tri(fi-chloroethyl)amine hydrochloride, in a molar proportion of 8:1, respectively, were heated together for 8 hours at 210 C. The product, tri[fl-(N-phenyl-N-ethylamino)ethyl] amine, was isolated in accordance with the procedure set forth in Example 1.

EXAMPLE 3 Tri lfl-(N-phenyl-N-isoamylamino) ethyl] amine Tri( 3-chloroethyl)amine hydrochloride, N-isoamylaniline, and tri-n-butylamine, in a molar proportion of 1:324, respectively, were reacted at 2l0220 C. for 8 hours. Then, the reaction mixture was made distinctly alkaline with a 10-per cent aqueous solution of sodium hydroxide and subjected to steam distillation until no more tri-nbutylamine distilled over. The residual was dissolved in diethyl ether and water-washed. Ether was removed by evaporation on the steam bath, leaving the compound, tri[B-(N-phenyl-N-isoamylamino)ethyl] amine.

Test data The mineral oil used for testing the compounds of this invention was a furfural-refined Mid-Continent (Rodessa) distillate stock having a specific gravity of 0.860, a flash point of 405 F., and a viscosity of 155 S. S. U. at 100 F. It is a lubricating oil suited for use in steam turbines. 7

EXAMPLE 4 The compounds described in Examples 1 through 3 were subjected to the Brown-Boveri Turbine Oil Test. This test is described in the Brown-Boveri Rev., 16 (-2), 92-7 (1929). In brief, a 200-milliliter sample of oil under test is placed in a 400-milliliter covered beaker containing a V-shaped piece of polished copper. Air is passed over the surface of the oil at a rate of 2 liters per hour. The test is carried out for 72 hours at 230 C. and then for 24 hours at room temperature. The results, in terms of condition of the copper, neutralization number (N. N.), and Lovibond color, indicate the oxidation stability of the oil tested. These results are compared with similar results for the uninhibited base oil. Pertinent test results for the compounds of Examples 1 through 3 are set forth in Table I.

TABLE I [Brown-Boveri Turbine Oil Oxidation Test (0.2%, by weight, of compound in base oil) I Neutralization number.

4 EXAMPLE 5 The compounds of Examples 2 and 3 were subjected to the ASTM Turbine Oil Oxidation Test. This test is fully described in the ASTM Manual, as Test D-943-47T. in general, the test involves placing a 300-milliliter sample of test oil in a tube provided with a gas inlet having a fritted glass outlet, and a catalyst coil consisting of interwound iron and copper wire. The test is conducted at a temperature of 203:0.9 F. Sixty milliliters of water are maintained in the tube, and oxygen is passed through the oil at the rate of 3 liters per hour. The test is continucd until periodic testing shows that the oil has greatly increased in acidity, a sign of the formation of acidic oxidation products. These data are usually plotted graphically. Color can also be noted, although acidity is the primary criterion in this test.

In addition to the uninhibited base oil (A), two other blends were subjected to this test. Blend R was a blend of 0.2 weight per cent of the compound of Example 2 in the base oil. Blend S was a blend of 0.2 per cent of the compound of Example 3 in the base oil. Pertinent test data for these runs are set forth in Table II.

in the figure, the acidity (N. N.) data for the runs reported in Table II are plotted graphically. As will be apparent from the curves for the base oil (curve A), the uninhibited oils rapidly undergo oxidation. The curve therefor is typical, in that the acidity of the oil remains low until oxidation commences. At that point, acidity increases rapidly, often within a matter of a few hours, causing a sharp rise in the curve. It will be noted that test blend R maintained in low acidity for well over days. It was not until 127 days that the rate of oxidation had increased to the point that acidic bodies had been formed to an appreciable extent.- Blend S remained stable for almost 100 days, and showed no deterioration due to oxidation until after about 102 days had passed.

The foregoing examples have illustrated the preparation of the compounds c'ontem'plat'e'd herein, and have demonstrated the efiective'ness' of typical compounds. It will be apparent therefrom that the compounds defined hereinbefore are efiective anti-oxidants, when blended in mineral lubricating oils in small amounts.

The amount of the compounds of this invention which is blended with a mineral lubricating oil varies between about 0.05 per cent and about 5 per cent, by weight. It is ordinarily preferred to use between about 0.1 per cent and about 2 per cent, by weight. Concentrates of these reaction products in mineral oils are contentplated.- Accordingly, more than 5 percent, and up to 49 per cent of the react-ion products (limited by the dispersibility thereof in mineral oil) might be blended in a mineral oil, which oil need not be the same type of oil that is ultimately used. Thus, a concentrate can be prepared in a light oil, such as a kerosene or light household oil. The concentrate can then be dissolved, in the requisite amount of the oil to be inhibited, in order to achieve a blend containing th'e'desired amount of additive.

Other oil addition agents can be used in conjunction with the additives of this invention, to improve other properties of the oil. For example, antirust agents, oiliness agents, V. I. improvers, pour point depressants; detergents, antifoamants, E. P". agents and the like can be added to the lubricating oil along with the additives of this invention. Such other additives are well known to those familiar with the art. Accordingly, it is believed unnecessary to list them here.

Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope thereof, as those skilled in the art will readily understand. Such variations and modifications are considered to be within the purview and scope of the appended claims.

What is claimed is:

l. A mineral lubricating oil containing a small amount, sufiicient to inhibit the oxidation tendencies thereof, of a compound having the formula,

R (YI TOH2OH2-)I-NR'a-n wherein Y is an unsubstituted phenyl radical, R and R are alkyl groups having between 1 and 8 carbon atoms, and n is an integer of between 2 and 3, inclusive.

2. A mineral lubricating oil containing between about 0.05 per cent, by weight, and about 5 per cent, by weight, of a compound having the formula,

wherein Y is an unsubstituted phenyl radical, R and R are alkyl groups having between 1 and 8 carbon atoms, and n is an integer of between 2 and 3, inclusive.

3. A mineral lubricating oil containing a small amount, suflicient to inhibit the oxidation tendencies thereof, of N,N-di 18-(N'-phenyl-N-ethylamino ethyl] -n-butylamine.

4. A mineral lubricating oil containing a small amount, sufiicient to inhibit the oxidation tendencies thereof, of tri 13- N-phenyl-N-ethylamino) ethyl] amine.

5. A mineral lubricating oil containing a small amount, sufiicient to inhibit the oxidation tendencies thereof, of tri 1S- (N-phenyl-N-isoamylamino) ethyl] amine.

References Cited in the file of this patent UN] IED STATES PATENTS Number Name Date 2,067,291 Salzberg Jan. 12, 1937 

1. A MINERAL LUBRICATING OIL CONTAINING A SMALL AMOUNT, SUFFICIENT TO INHIBIT THE OXIDATION TENDENCIES THEREOF, OF A COMPOUND HAVING THE FORMULA, 